a. Field of the Invention
This invention relates to a method and a system for supplying clock signals, and more particularly relates to a clock signal supplying method and system suitable for use in a clock supply section of a large-scale computer capable of carrying out arithmetic operations at a high speed.
b. Background Art
As a conventional method for adjusting phases of clock signals for a large-scale computer, there has generally been known a method in which the waveform of a clock signal is manually observed at each destination with oscilloscopes or the like and its phase is adjusted to that of a predetermined value. Other than the method using an oscilloscope, Japanese Patent Application Laid-Open Publication (Kokai) No. 61-39619 discloses a method which uses a ring oscillator formed by a clock supply circuit and detects signal delay time of the clock supply circuit from the oscillation frequency to adjust the same to a predetermined value.
However, these conventional methods are detrimental: the former method in which the phase adjustment of a clock signal is carried out manually with an oscilloscope or the like requires considerable time and trouble for adjustment and the number of points where the adjustment is made should be restricted. Consequently, the adjustment should be conducted at centralized relay points in the number of several tens to several hundreds, and signals must be transmitted to the terminal destinations positioned further ahead without adjustment. Possible variations in propagation time of the signals which are transmitted without adjustment would set a limitation in reduction of clock skews. If the adjustment currently conducted by hand is to be automated, it is necessary to make consecutively a probe to contact waveform observation points corresponding to respective adjustment points. This would require a mechanical positioning device.
If the adjusting points are large in number, contacts become congested, and the probe must be positioned with a high precision. Besides the precision requirement, speed should be high, thus posing further difficulty in realization of the system. If a signal line for the probe is provided separately for each observation point respectively, then mechanical positioning will not be necessary any more, but all the signal propagation times for the signal lines of the probe connected to the respective observation points should be set equal to each other. In order to make all of them identical, there will be needed all the same cumbersome operation as that of the adjustment of phases of clock signals, which requires many hands.
Above mentioned method of Kokai No. 61-39619 is also detrimental in that it has the similar problem to that of the former conventional method because all the signal propagation times should be uniform for the cables by which signals are fed back from destinations to input ends. In a large-scale computer, especially, machine cycle will be shortened more and more as the arithmetic operation increases its speed. Therefore, the phase adjustment points should be increased in number to reduce clock skews. The above mentioned problems will further present formidable difficulties in this context.